The invention relates to a device for an interferometric measuring of as well as a method for an interferometric measuring of an object.
Devices and methods for an interferometric measuring of an object are known in various embodiments: For example a typical design of a laser-Doppler vibrometer is known, which comprises a laser as the radiation source to generate a source beam, a beam splitter device to split the source beam into a measuring beam and a reference beam, an optic interference device, and a first detector.
The measuring beam is guided to a measuring point on the object and the at least partially reflected measuring beam (called “receiver beam”) is interfered together with the reference beam on the detector surface of the detector such that by assessing the interference signal conclusions can be drawn, for example regarding a motion of the object surface at the measuring point in the direction of the optic axis of the measuring beam.
Furthermore, arrangements are known, which show a heterodyne structure. Here, typically via a Bragg-cell a frequency shift is caused between the reference beam and the measuring beam. In general, by the interference of the interfered measuring and reference beam an intensity modulation occurs with the frequency of the difference frequency of the two beams. In a heterodyne design the difference frequency of the frequency shift introduced with the Bragg-cell and the Doppler-shift is created by the motion of the object. The frequency shift introduced in the heterodyne design serves in the electrical sense as a carrier frequency, which is frequency modulated by the speed of the object and/or is phase modulated by distance changes of the object.
By way of phase modulation of the modulated carrier signal the movement of the object can therefore be displayed in the distance coordinate. By the frequency modulation of the modulated carrier signal the speed of the object can be displayed.